difficulty in circuit

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naik_mc

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i have tried to work with the circuit attached for the basic intercom system but it doesn't run i.e work. i can't dind out where the problem is. please if anyone can help with this.
 

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  • ckt diagram for simple intercom.gif
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Please provide more information.

What do you mean it doesn't work?

Have you check all the connections?

Does it oscillate?

Have you measured the voltages at different parts of the circuit and compared them to what you'd expect?
 
naik_mc said:
i have tried to work with the circuit attached for the basic intercom system but it doesn't run i.e work. i can't find out where the problem is. please if anyone can help with this.
Click to expand...

Please indicate the way in which you operates the switches for
(a). master to speak and slave to listen
and (b). Slave to speak and master to listen.
I fear that you may not be operating the equipment properly.
 
yes i have checked all the connections and i have done the connections 2 to 3 times. The voltages do not reach to the speakers.
 
Naik, Please see the modified diagram.

I have indicated the changes. It will work.

1. if S1 is pressed (S1a,b&c), Master will speak and slave will listen.

2. If S2 is pressed, Slave will speak and master would listen.
 
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The 8R2 resistor at the output of the LM380 amplifier keeps the circuit from freezing to death.

The one at the input keeps the speaker from resonating too much.

The datasheet for the LM380 shows an RC network to ground that must be used at its output. This circuit doesn't have it.
 
audioguru said:
The 8R2 resistor at the output of the LM380 amplifier keeps the circuit from freezing to death.
Click to expand...
You mush be being sarcastic.

Shouldn't it form a zobel network?

It should go to 0V via a 100nF capacitor.
 
The circuit shows an 8.2 ohm resistor in series with the output of the LM380 amplifier. It doesn't show Zobel network parts connected correctly.

The output speaker will also resonate a lot the way it is shown. Like a bongo drum.
 
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